Is a photo editor or vector graphics software essential for 3D creation and Modeling
There is no such a rule.  In fact there are no rules at all here. It depends on what you want to do. No software is essential in digital art. You can use whatever you want or like and whatever gives you the desired results. With that said it is a fact that photo or image editing software is extremely useful when working with 3d. 

Having worked with Photoshop almost every single day of my life for the last 15 years or so I can say... that it does not necessarily need to be Photoshop :D . It's a good and popular choice, but you can definitely find good or even better alternatives. You can choose Krita, Affinity Photo, Gimp or even do some painting straight in Blender, but Photoshop will do as well. Or don't choose at all, use all of them that you can get your hands on. As for you not wishing to spend time on it... Well I would recommend not to think too much about it. You will not waste that time and you should be prepared to spend loads and loads of time if you are learning CG anyway. The main concepts are pretty similar in most image editing software packages and will be useful whatever you choose. In 3d graphics context, image editors are relatively simple, so it's definitely not a bad idea to just choose one and learn it. Don't make a big deal out of it.